THE STABILITY AND STRUCTURE OF COMPLEX SPECIES FORMED IN EQUILIBRIUM REACTIONS OF DIETHYLTIN(IV) WITH N-D-GLUCONYLAMINO ACIDS IN AQUEOUS-SOLUTION

Complex formation equilibria of diethyltin(IV) with five N-D-gluconyla mino acids in aqueous solution (I = 0.1 M, NaClO4) were studied and th e stabilities of the species were determined by potentiometric titrati ons. Diethyltin(IV) complexes of a-amino acid derivatives are water-so luble in the physiological pH range, while in the presence of N-D-gluc onyl-beta-alanine a precipitate is formed, which dissolves with increa sing pH. C-13 NMR measurements showed that in the N-D-gluconyl-alpha-a mino acid complexes the ligand is coordinated through its deprotonated carboxylate oxygen, amide nitrogen and C(2)-hydroxy group, while for the soluble N-D-gluconyl-beta-alanine complex the ligand is coordinate d via the deprotonated carboxylate and C(3)-, C(4)-, C(5)-hydroxy grou ps. Mossbauer measurements reflected the geometry of the complexes for med.